usb: gadget: f_uac2: reset wMaxPacketSize

usb: gadget: f_uac2: reset wMaxPacketSize

commit 9389044f27081d6ec77730c36d5bf9a1288bcda2 upstream.

With commit 913e4a90b6f9 ("usb: gadget: f_uac2: finalize wMaxPacketSize according to bandwidth")
wMaxPacketSize is computed dynamically but the value is never reset.

Because of this, the actual maximum packet size can only decrease each time
the audio gadget is instantiated.

Reset the endpoint maximum packet size and mark wMaxPacketSize as dynamic
to solve the problem.

Fixes: 913e4a90b6f9 ("usb: gadget: f_uac2: finalize wMaxPacketSize according to bandwidth")
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20201221173531.215169-2-jbrunet@baylibre.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>